This invention relates generally to parachute assemblies, and more particularly to such assemblies somewhat similar to that disclosed in U.S. Pat. No. 2,537,152 to Moran but differing therefrom in certain critically important features of a distinguishing character.
In a stowage system such as that of the Moran patent, the canopy is folded or rolled into an elongated shape with the skirt of the canopy at one end and the apex of the canopy at the other end. A panel of flexible sheet material is permanently attached to the canopy of the parachute and is folded over on itself to enclose the skirt end of the elongated shape.
The suspension lines of the parachute are grouped into a rope-like bundle, and the bundle is formed into a zigzag configuration to cooperate with yielding fasteners on the panel to keep the latter closed around the skirt end of the elongated shape. The remainder of the elongated shape is folded back onto the closed panel to form therewith a compact package, which is encased in the usual releasable manner in a parachute container for use by a jumper.
When the jumper opens the parachute container, the airstream stretches out the canopy first, then the folds of the rope-like bundle of suspension lines pull free from the yieldable fasteners of the panel to permit the suspension lines to stretch out and finally open the closed panel to free the canopy skirt for prompt inflation of the canopy.
A serious difficulty arises in the use of many parachute assemblies in that the airstream rams into the skirt of the canopy to tend to inflate the canopy prematurely; i.e., before the suspension lines are fully extended. Such premature inflation of the canopy tightens the slack suspension lines with a severe jolt that is hard on the jumper and subjects the parachute structure to damaging stresses. Another result of premature inflation is that the nylon suspension lines may rub on the nylon canopy to burn the canopy. Such a burn can spread into an extensive tear that may increase the rate of descent of the jumper unduly and result in a hard landing and possible injury to the jumper. Another result of premature inflation is that the slack suspension lines may wrap around the inflated canopy to cause hazardous instability of the canopy.
Certain attempts have been made in the prior art to prevent premature canopy inflation. The Moran patent, for example, teaches folding a special panel over the skirt end of the canopy when the canopy is formed into an elongated shape for stowage. This expedient has been found somewhat unsatisfactory, because there are liberal gaps in the leading edge of the folded panel, and when the jumper falls through space, the airstream passes through these gaps to enter the canopy skirt with ram action to cause the stowed canopy to balloon to bulbous shape.
The U.S. Pat. No. 3,690,604 (to Guilfoyle) teaches reefing the skirt of the stowed canopy; i.e., embracing the skirt end of the stowed canopy with a tight band that is intended to keep air from entering the skirt prematurely. The reefing, however, does not actually preclude the entrance of the airstream into the embraced skirt, with the result that the stowed canopy balloons to the bulbous shape shown in some of the drawings of the Guilfoyle patent. Reefing the skirt of the canopy, moreover, complicates the deployment procedure in that it makes necessary some provision for releasing the reefing when the suspension lines become fully stretched out.
It is apparent that there is a definite need for some means to absolutely prevent entrance of the airstream into the stowed canopy until the suspension lines are fully stretched out.